CN113491024A

CN113491024A - Solid polymer electrolyte membrane, membrane electrode assembly, and solid polymer fuel cell

Info

Publication number: CN113491024A
Application number: CN202080017047.2A
Authority: CN
Inventors: 奥山匠; 平居丈嗣
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2019-02-28
Filing date: 2020-02-28
Publication date: 2021-10-08
Also published as: US11996595B2; EP3932960A4; US20210391590A1; WO2020175675A1; JP7416046B2; EP3932960A1; JPWO2020175675A1

Abstract

Disclosed is a method for producing a solid polymer which is excellent in power generation characteristics and hydrogen gas utilization efficiencyA solid polymer electrolyte membrane for a fuel cell, and a membrane electrode assembly and a solid polymer fuel cell obtained using the same. The solid polymer electrolyte membrane of the present invention has a hydrogen gas permeability coefficient of 2.4X 10 at a temperature of 80 ℃ and a relative humidity of 10%^‑9cm³·cm/(s·cm²cmHg) or less, and a film thickness of 7 to 20 μm.

Description

Solid polymer electrolyte membrane, membrane electrode assembly, and solid polymer fuel cell

Technical Field

The present invention relates to a solid polymer electrolyte membrane, a membrane electrode assembly, and a solid polymer fuel cell.

Background

The polymer electrolyte fuel cell has a structure in which a membrane electrode assembly is sandwiched between 2 separators to form a cell, and a plurality of cells are stacked. The membrane electrode assembly includes: an anode and a cathode having a catalyst layer, and a solid polymer electrolyte membrane disposed between the anode and the cathode. The solid polymer electrolyte membrane is obtained by, for example, forming a polymer having an acid-type sulfonic acid group into a membrane.

In the examples of patent document 1, it is disclosed that CF is used as a polymer having an acid sulfonic acid group₂＝CFOCF₂CF(CF₃)OCF₂CF₂SO₂Copolymerization of F with tetrafluoroethylene to obtain a polymer₂And a perfluoropolymer obtained by acidifying the group represented by F.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2002-216804

Disclosure of Invention

Problems to be solved by the invention

In recent years, there has been a demand for further improvement in the performance of polymer electrolyte fuel cells, and specifically, there has been a demand for polymer electrolyte fuel cells having excellent power generation characteristics and excellent utilization efficiency of hydrogen gas as fuel.

The present inventors evaluated a solid polymer electrolyte membrane comprising the above-described perfluoropolymer described in patent document 1 as an electrolyte and found that: there is room for improvement in at least one of the power generation characteristics and the hydrogen gas utilization efficiency of a polymer electrolyte fuel cell.

In view of the above circumstances, an object of the present invention is to provide a polymer electrolyte membrane that can produce a polymer electrolyte fuel cell having excellent power generation characteristics and hydrogen gas utilization efficiency, and a membrane electrode assembly and a polymer electrolyte fuel cell obtained using the same.

Means for solving the problems

The present inventors have intensively studied the above problems and, as a result, have found that: the present inventors have completed the present invention by finding that a solid polymer electrolyte fuel cell having excellent power generation characteristics and hydrogen gas utilization efficiency can be produced by using a solid polymer electrolyte membrane comprising a polymer electrolyte having a hydrogen gas permeability coefficient of not more than a predetermined value and having a membrane thickness within a predetermined range.

Namely, the present inventors have found that: the above problems can be solved by the following configurations.

[1]A solid polymer electrolyte membrane comprising a polymer electrolyte having a hydrogen permeability coefficient of 2.4 x 10 at a temperature of 80 ℃ and a relative humidity of 10%^-9cm³·cm/(s·cm²cmHg) or less,

the thickness of the solid polymer electrolyte membrane is 7-20 μm.

[2] The solid polymer electrolyte membrane according to [1], wherein the polymer electrolyte is a perfluoropolymer having an acid sulfonic acid group.

[3] The solid polymer electrolyte membrane according to [2], wherein the perfluoropolymer comprises a perfluoromonomer unit comprising at least 1 unit selected from the group consisting of a perfluorovinyl ether unit and a perfluoroallyl ether unit.

[4] The solid polymer electrolyte membrane according to [2] or [3], wherein the perfluoropolymer contains substantially no at least 1 unit selected from the group consisting of a unit having a halogen atom other than a fluorine atom, a unit having a ring structure, and a unit having a crosslinked structure formed by covalent bonds.

[5]According to [3]Or [4 ]]The solid polymer electrolyte membrane according to (1), wherein the perfluoroallyl ether unit is a unit represented by the following formula A-1. In the formula A-1 described later, R^F1And R^F2Each independently a C1-3 perfluoroalkylene group.

[6] The solid polymer electrolyte membrane according to any one of [3] to [5], wherein the perfluoromonomer unit further comprises a tetrafluoroethylene unit.

[7] The solid polymer electrolyte membrane according to any one of [1] to [6], wherein the polymer electrolyte has an ion exchange capacity of 1.4 to 2.5 meq/g of dry resin.

[8] A membrane-electrode assembly comprising: an anode having a catalyst layer, a cathode having a catalyst layer, and any one of the solid polymer electrolyte membranes of [1] to [7] disposed between the anode and the cathode.

[9] A membrane electrode assembly according to [8], wherein the catalyst layer of the cathode comprises a catalyst and a polymer having an ion exchange group,

the value obtained by subtracting the hydrogen gas permeability coefficient of the polymer electrolyte from the hydrogen gas permeability coefficient of the polymer having ion exchange groups was 1.0X 10^-8cm³·cm/(s·cm²cmHg) or more.

[10] A solid polymer fuel cell comprising the membrane electrode assembly according to [8] or [9 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a polymer electrolyte membrane capable of producing a polymer electrolyte fuel cell having excellent power generation characteristics and hydrogen gas utilization efficiency, and a membrane electrode assembly and a polymer electrolyte fuel cell obtained using the same.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a membrane electrode assembly of the present invention.

Detailed Description

The following definitions of terms apply to the present specification and claims unless otherwise specified.

The "ion exchange group" refers to a group capable of exchanging at least a part of ions contained in the group with other ions, and examples thereof include the following sulfonic acid type functional group and carboxylic acid type functional group.

The "sulfonic acid type functional group" is an acid type sulfonic acid group (-SO)₃H) And salt type sulfonic acid group (-SO)₃M². Wherein M is²Alkali metal or quaternary ammonium cations).

"carboxylic acid type functional group" is an acid type carboxylic acid group (-COOH) and a salt type carboxylic acid group (-COOM)¹. Wherein M is¹Alkali metal or quaternary ammonium cations).

By "precursor membrane" is meant a membrane comprising a polymer having groups that can be converted to ion exchange groups.

The "group capable of being converted into an ion exchange group" refers to a group capable of being converted into an ion exchange group by a hydrolysis treatment, an acid formation treatment, or the like, and is sometimes referred to as a "precursor group".

The "group capable of being converted into a sulfonic acid type functional group" means a group capable of being converted into a sulfonic acid type functional group by a hydrolysis treatment, an acid type treatment or the like.

The "group convertible into a carboxylic acid type functional group" means a group convertible into a carboxylic acid type functional group by a known treatment such as hydrolysis treatment or acid type treatment.

The term "substantially no unit" means that the content of the unit is 1 mol% or less based on the total units of the polymer including the unit.

"Unit" in a polymer refers to a radical derived from 1 molecule of a monomer formed by polymerization of the monomer. The unit may be a radical formed directly by polymerization reaction, or may be a radical in which a part of the radical is converted into another structure by treating a polymer obtained by polymerization reaction. The structural units derived from the respective monomers may be described by names in which "units" are given to the monomer names.

The unit represented by the formula A-1 is referred to as a unit A-1. Units represented by other formulae are also described.

The compound represented by the formula 1-1 is referred to as compound 1-1. The compounds represented by the other formulae are also described in the same manner.

[ solid Polymer electrolyte Membrane ]

The solid polymer electrolyte membrane of the present invention (hereinafter also referred to simply as "electrolyte membrane") comprises a hydrogen gas permeability coefficient of 2.4X 10 under conditions of a temperature of 80 ℃ and a relative humidity of 10%^-9cm³·cm/(s·cm²cmHg) or less, wherein the solid polymer electrolyte membrane has a membrane thickness of 7 to 20 μm.

According to the electrolyte membrane of the present invention, a polymer electrolyte fuel cell having excellent power generation characteristics and hydrogen gas utilization efficiency can be produced. The detailed reason is not clear, but is presumed to be for the following reason.

A polymer electrolyte fuel cell generates electricity by supplying an oxygen-containing gas to a cathode and a hydrogen-containing gas to an anode. When the hydrogen-containing gas supplied to the anode passes through the electrolyte membrane and moves to the cathode side (so-called crossover of hydrogen gas), there is a problem that the hydrogen gas utilization efficiency of the polymer electrolyte fuel cell decreases.

In view of this problem, the present inventors have found that: if an electrolyte membrane containing a polymer electrolyte having a hydrogen gas permeability coefficient of not more than a predetermined value is used, the crossover of hydrogen gas can be suppressed, and as a result, a fuel cell having excellent hydrogen gas utilization efficiency can be obtained.

On the other hand, the present inventors have found that: by setting the hydrogen permeability coefficient to a predetermined value or less, the power generation characteristics of the polymer electrolyte fuel cell are slightly improved, but there is room for improvement.

In view of this problem, the present inventors have found that: when the film thickness of the electrolyte membrane is within a predetermined range, the resistance of the electrolyte membrane is sufficiently reduced, and as a result, a solid polymer fuel cell having excellent power generation characteristics can be obtained. Namely, it is presumed that: the effect of having the hydrogen gas permeability coefficient of the polymer electrolyte equal to or less than the predetermined value and the effect of having the film thickness of the electrolyte membrane within the predetermined range act synergistically, and a solid polymer fuel cell having excellent power generation characteristics can be obtained.

< polyelectrolyte >

The polymer electrolyte is not particularly limited as long as it is an electrolyte formed of a polymer having a hydrogen permeability coefficient satisfying the range described below, and a perfluoropolymer having an acid-type sulfonic acid group (hereinafter also simply referred to as "polymer H") is preferable from the viewpoint of further improving the power generation characteristics of the solid polymer fuel cell.

The polymer H preferably contains a perfluoromonomer unit from the viewpoint of excellent durability of the electrolyte membrane.

From the viewpoint of more excellent power generation characteristics of the polymer electrolyte fuel cell, the perfluoromonomer unit preferably contains at least 1 unit (hereinafter also referred to as "unit a") selected from the group consisting of a perfluorovinyl ether unit and a perfluoroallyl ether unit.

The unit a may contain one or both of a perfluorovinyl ether unit and a perfluoroallyl ether unit, and from the viewpoint of ease of synthesis, it preferably contains a perfluoroallyl ether unit, and particularly preferably contains a perfluoroallyl ether unit.

The unit contained in the unit a preferably has an ion exchange group, more preferably a sulfonic acid functional group, and particularly preferably an acid type sulfonic acid functional group, from the viewpoint that the resistance of the electrolyte membrane is low and the power generation characteristics of the polymer electrolyte fuel cell are more excellent.

When each unit included in the unit a has an ion exchange group, the number of ion exchange groups in each unit is preferably 2 or more, and particularly preferably 2 from the viewpoint of ease of synthesis, from the viewpoint of reduction in the electrical resistance of the electrolyte membrane and further improvement in the power generation characteristics of the polymer electrolyte fuel cell.

The perfluoroallyl ether unit is preferably the unit A-1 from the viewpoint of easily obtaining a polymer electrolyte having a hydrogen gas permeability coefficient within the range described below.

The perfluorovinyl ether unit is preferably the unit A-2 or the unit A-3, from the viewpoint of easily obtaining a polymer electrolyte having a hydrogen gas permeability coefficient within the range described below.

In the formulae A-1 to A-3, R^F1And R^F2Each independently a C1-3 perfluoroalkylene group.

As R^F1And R^F2Specific examples of (A) include-CF₂-、-CF₂CF₂-、-CF(CF₃)-、-CF₂CF₂CF₂-、-CF(CF₂CF₃)-、-CF(CF₃)CF₂-、-CF₂CF(CF₃)-、-C(CF₃)(CF₃)-。

From the viewpoints of low cost of raw materials, easy production, and further improvement in ion exchange capacity of the polymer H, R^F1And R^F2Each independently is preferably a perfluoroalkylene group having 1 or 2 carbon atoms. In the case of the carbon number 2, the linear chain is preferable. Specifically, it is preferably-CF₂-、-CF₂CF₂-or-CF (CF)₃) -, more preferably-CF₂-or-CF₂CF₂-CF is particularly preferred₂-。

In the formula A-2, R^F3Is a C1-6 perfluoroalkylene group.

As R^F3Specific examples of (A) include-CF₂-、-CF₂CF₂-、-CF(CF₃)-、-CF₂CF₂CF₂-、-CF(CF₂CF₃)-、-CF(CF₃)CF₂-、-CF₂CF(CF₃)-、-C(CF₃)(CF₃)-、-CF₂CF(CF₃)OCF₂CF(CF₃)-。

From the viewpoints of low cost of raw materials, easy production, and further improvement in ion exchange capacity of the polymer H, R^F3Preferably a C1-3 perfluoroalkylene group. Specifically, it is preferably-CF₂-、-CF₂CF₂-or-CF₂CF(CF₃) -CF is particularly preferred₂CF(CF₃)-。

In the formula A-2, m is 0 or 1.

The perfluoromonomer unit may comprise units other than unit a. As the units other than the unit A, perfluoromonomer units having no ion exchange group and its precursor group are exemplified.

Specific examples of the perfluoromonomer unit having no ion exchange group or precursor group thereof include a tetrafluoroethylene (hereinafter also referred to as "TFE") unit and a hexafluoropropylene unit, and the TFE unit is preferable from the viewpoint of excellent strength of the electrolyte membrane.

The lower limit of the content of the unit a is preferably 7 mol%, more preferably 8 mol%, and particularly preferably 9 mol% with respect to all units in the polymer H, from the viewpoint of easily setting the ion exchange capacity of the electrolyte membrane to a range described below and from the viewpoint of easily obtaining a polymer electrolyte having a hydrogen gas permeability coefficient in a range described below.

From the viewpoint of excellent strength of the electrolyte membrane, the upper limit of the content of the unit a is preferably 45 mol%, more preferably 36 mol%, and particularly preferably 22 mol% with respect to all units in the polymer H.

When the polymer contains a perfluoromonomer unit having no ion exchange group or precursor group thereof, the content thereof is preferably 55 to 93 mol%, more preferably 65 to 92 mol%, and particularly preferably 78 to 91 mol% based on the total units in the polymer H. These levels are particularly suitable when the perfluoromonomer units are TFE units.

The polymer H preferably contains substantially no unit having a halogen atom other than a fluorine atom (hereinafter also referred to as "unit X1"). Thus, a chain transfer reaction is less likely to occur when the monomer is polymerized to produce the polymer H, and the amount of oligomer produced during production is small.

Specific examples of the unit X1 include a chlorotrifluoroethylene unit, a bromotrifluoroethylene unit, a iodotrifluoroethylene unit, and a dichlorodifluoroethylene unit.

The fact that the polymer H contains substantially no unit X1 means that the content of the unit X1 is 1 mol% or less, preferably not (0 mol%) based on the total units in the polymer H.

The polymer H preferably contains substantially no unit having a ring structure (hereinafter also referred to as "unit X2"). This can prevent the polymer H from becoming brittle and can increase the toughness of the polymer H, and therefore an electrolyte membrane obtained using the polymer H has excellent mechanical strength.

Examples of the ring structure include an aliphatic hydrocarbon ring, an aliphatic heterocyclic ring, an aromatic hydrocarbon ring, and an aromatic heterocyclic ring. The ring structure may be present in the main chain or in the side chain.

Specific examples of the unit X2 include units having a cyclic ether structure described in Japanese patent No. 4997968 and Japanese patent No. 5454592.

The meaning of the polymer H substantially free of the unit X2 is the same as that of the unit X1, preferably free of it (0 mol%).

The polymer H preferably contains substantially no unit having a cross-linked structure formed by covalent bonds (hereinafter also referred to as "unit X3"). Thus, the polymer H is easily dissolved or dispersed in the liquid medium, and therefore, when an electrolyte membrane is formed using a liquid composition containing the polymer H and the liquid medium, the electrolyte membrane can be made into a thin film.

The crosslinked structure formed by covalent bonds means: a structure obtained by polymerizing a monomer having a crosslinkable group (e.g., vinyl group, perfluorovinyl group, etc.) capable of being crosslinked by a covalent bond and then crosslinking the crosslinkable group by a covalent bond; alternatively, the structure is obtained by crosslinking a monomer having a crosslinkable group capable of crosslinking by a covalent bond simultaneously with the polymerization reaction.

Specific examples of the unit X3 include units having the following structures: a structure obtained by polymerizing a compound of the formulae 8 to 15 (compound having 2 crosslinkable groups) described in Japanese patent laid-open No. 2001-176524, and then crosslinking the crosslinkable groups not used in the polymerization via covalent bonds.

The meaning of the polymer H substantially free of the unit X3 is the same as that of the unit X1, preferably free of (0 mol%).

(method for producing Polymer electrolyte)

The method for producing the polymer electrolyte will be described by taking the method for producing the polymer H as an example.

Examples of the method for producing the polymer H include: the acid sulfonic acid group in the polymer H is used as a precursor group (specifically-SO)₂Group represented by F) into an acid type sulfonic acid group (-SO) (hereinafter also referred to as "polymer F") (the precursor group of the precursor polymer is converted into a sulfonic acid group (-SO) ₃ ^-H⁺) The method of (1).

as-SO to be a precursor group₂Specific examples of the method for converting the group represented by F into an acid-type sulfonic acid group include: reacting the-SO of the polymer F₂And F, hydrolyzing the group to prepare a salt-type sulfonic acid group, and converting the salt-type sulfonic acid group into an acid-type sulfonic acid group by converting the salt-type sulfonic acid group into the acid-type sulfonic acid group.

The polymer F preferably comprises perfluoromonomer units and has-SO₂Perfluoropolymer of the group represented by F.

The perfluoromonomer unit in the polymer F preferably contains at least 1 unit (hereinafter also referred to as "unit a") selected from the group consisting of a perfluorovinyl ether unit and a perfluoroallyl ether unit.

The units contained in the units a may have a precursor group of an ion exchange group or may not have a precursor group of an ion exchange group, preferably a precursor group having an ion exchange group, and particularly preferably a sulfonic acid type functional groupPrecursor group of (2) (in particular-SO)₂The group represented by F).

Specific examples of the perfluorovinyl ether unit in the unit a include conversion of an acid-type sulfonic acid group of the perfluorovinyl ether unit in the unit A into-SO ₂Units of the group represented by F.

The perfluoroallyl ether unit in the unit a is preferably a unit a-1.

R in the formula a-1^F1And R^F2Are respectively reacted with R in the formula A-1^F1And R^F2Have the same meaning.

The perfluoromonomer units in unit a may comprise units other than unit a. Specific examples of the unit other than the unit a include perfluoromonomer units having no ion exchange group and its precursor group.

Specific examples of the perfluoromonomer unit having no ion exchange group and its precursor group are the same as those of polymer H.

The content of each unit in the polymer F is preferably the same as the content of each unit in the polymer H.

The polymer F preferably contains substantially no at least 1 unit selected from the group consisting of a unit having a halogen atom other than a fluorine atom, a unit having a ring structure, and a unit having a crosslinked structure formed by covalent bonds, and particularly preferably contains substantially no all of them.

Specific examples of the unit having a halogen atom other than a fluorine atom, the unit having a ring structure, and the unit having a crosslinked structure formed by covalent bonds are the same as the polymer H.

The term "substantially free" means the same meaning as in the case of the polymer H.

The polymer F preferably has a volumetric flow rate value (hereinafter also referred to as "TQ value") of 220 ℃ or higher, more preferably 225 to 360 ℃, and still more preferably 230 to 350 ℃. If the TQ value is not less than the lower limit, the polymer H having a sufficient molecular weight can be obtained, and therefore the strength of the electrolyte membrane is excellent. If the TQ value is not more than the upper limit, the solubility or dispersibility of the polymer H in a liquid medium is improved, and therefore, a liquid composition can be easily produced. The TQ value is an indicator of the molecular weight of the polymer F.

The "TQ value" of the polymer F can be determined by the method described in the section of the examples below.

< Properties >

The hydrogen permeability coefficient of the polyelectrolyte under the conditions of 80 ℃ and 10% relative humidity is 2.4 multiplied by 10^-9cm³·cm/(s·cm²cmHg) or less, preferably 2.2X 10^-9cm³·cm/(s·cm²cmHg) or less, more preferably 2.0X 10^-9cm³·cm/(s·cm²cmHg) or less, particularly preferably 1.8X 10^-9cm³·cm/(s·cm²cmHg) or less. If the hydrogen gas permeability coefficient is not more than the upper limit value, the crossover of hydrogen gas can be suppressed.

From the viewpoint of reducing the resistance value of the electrolyte membrane and further improving the power generation characteristics of the solid polymer fuel cell, the hydrogen gas permeability coefficient of the polymer electrolyte at a temperature of 80 ℃ and a relative humidity of 10% is preferably 1.0 × 10 ^-12cm³·cm/(s·cm²cmHg) or more, particularly preferably 1.0X 10^-11cm³·cm/(s·cm²cmHg) or more.

The "hydrogen gas permeability" of the polymer electrolyte was determined by the method described in the section of the example below, using a film having a thickness of 25 μm and formed from the polymer electrolyte.

The ion exchange capacity of the polymer electrolyte is preferably 1.4 to 2.5 milliequivalents/g of dry resin, more preferably 1.6 to 2.4 milliequivalents/g of dry resin, and particularly preferably 1.8 to 2.3 milliequivalents/g of dry resin. If the ion exchange capacity of the polymer electrolyte is not less than the lower limit, the resistance of the electrolyte membrane obtained using the polymer electrolyte can be reduced, and as a result, the power generation characteristics of the solid polymer fuel cell can be further improved. When the ion exchange capacity of the polymer electrolyte is not more than the upper limit, the strength of the electrolyte membrane is excellent.

The "ion exchange capacity" of the polymer electrolyte can be determined by the method described in the section of examples below.

The electrolyte membrane has a film thickness of 7 to 20 μm, the lower limit of the above range is preferably 10 μm, particularly preferably 13 μm, and the upper limit of the above range is preferably 18 μm. If the film thickness of the electrolyte membrane is equal to or more than the lower limit of the above range, the crossover of hydrogen gas can be further suppressed, and the mechanical strength is excellent.

The film thickness of the electrolyte membrane is an average film thickness determined by the method described in the first section of the example described later.

< other materials >

The electrolyte membrane may be reinforced with a reinforcing material. Specific examples of the reinforcing material include porous bodies, fibers, woven fabrics, and nonwoven fabrics.

The reinforcing material is preferably composed of a material selected from the group consisting of polytetrafluoroethylene (hereinafter also referred to as "PTFE"), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter also referred to as "PFA"), polyether ether ketone (hereinafter also referred to as "PEEK"), and polyphenylene sulfide (hereinafter also referred to as "PPS").

In order to further improve durability, the electrolyte membrane may include 1 or more metals, metal compounds, or metal ions selected from the group consisting of cerium and manganese. Cerium and manganese decompose hydrogen peroxide, which is a causative substance for causing deterioration of the electrolyte membrane.

As the water retention agent for preventing drying, the electrolyte membrane may contain silica or heteropolyacid (e.g., zirconium phosphate, phosphomolybdic acid, phosphotungstic acid).

< use >

The electrolyte membrane can be suitably used as a solid polymer electrolyte membrane of a solid polymer fuel cell.

< method for producing electrolyte Membrane >

An example of the method for producing the electrolyte membrane is a method (casting method) in which a liquid composition described later is applied to the surface of a base film or a catalyst layer and dried.

As an example of a method for producing the electrolyte membrane containing the reinforcing material, a method in which the reinforcing material is impregnated with a liquid composition described later and dried is given.

In order to stabilize the electrolyte membrane, heat treatment is preferably performed. The heat treatment temperature varies depending on the kind of the polymer electrolyte, and is preferably 130 to 200 ℃. When the heat treatment temperature is 130 ℃ or higher, the water content of the polymer electrolyte becomes appropriate. When the heat treatment temperature is 200 ℃ or lower, thermal decomposition of the sulfonic acid group can be suppressed, and excellent conductivity of the electrolyte membrane can be maintained.

The electrolyte membrane may be treated with an aqueous hydrogen peroxide solution as necessary.

(liquid composition)

The liquid composition preferably comprises a polyelectrolyte and a liquid medium. The polyelectrolyte in the liquid composition may be dispersed in the liquid medium or may be dissolved in the liquid medium.

Specific examples of the liquid medium include water and an organic solvent. The liquid medium may be water alone, or an organic solvent alone, or a mixed solvent of water and an organic solvent, preferably a mixed solvent of water and an organic solvent.

When water is contained as the liquid medium, the dispersibility or solubility of the polymer electrolyte with respect to the liquid medium is likely to be improved. When an organic solvent is contained as a liquid medium, an electrolyte membrane that is not easily broken is easily obtained.

The organic solvent is preferably an alcohol having 1 to 4 carbon atoms, from the viewpoint of easily obtaining an electrolyte membrane that is not easily broken.

Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2,2, 2-trifluoroethanol, 2,2,3,3, 3-pentafluoro-1-propanol, 2,2,3, 3-tetrafluoro-1-propanol, 1,1,1,3,3, 3-hexafluoro-2-propanol, and 3,3, 3-trifluoro-1-propanol.

The organic solvent may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

When the liquid medium is a mixed solvent of water and an organic solvent, the content of water is preferably 10 to 99% by mass, and particularly preferably 20 to 99% by mass, based on the total mass of the liquid medium.

When the liquid medium is a mixed solvent of water and an organic solvent, the content of the organic solvent is preferably 1 to 90% by mass, and particularly preferably 1 to 80% by mass.

If the content of water and the organic solvent is within the above range, an electrolyte membrane which is excellent in dispersibility or solubility of the polymer electrolyte in a liquid medium and is less likely to break can be easily obtained.

The content of the polyelectrolyte is preferably 1 to 50% by mass, and particularly preferably 3 to 30% by mass, based on the total mass of the liquid composition. If the lower limit of the above range is not less than the above range, a film having a thickness can be stably obtained during film formation. If the viscosity of the liquid composition is not more than the upper limit of the above range, the viscosity of the liquid composition becomes appropriate.

In order to further improve the durability of the electrolyte membrane made of the liquid composition, the liquid composition may include 1 or more metals, metal compounds, or metal ions selected from the group consisting of cerium and manganese.

[ Membrane electrode Assembly ]

The membrane electrode assembly of the present invention comprises: the fuel cell includes an anode having a catalyst layer, a cathode having a catalyst layer, and the electrolyte membrane disposed between the anode and the cathode.

Since the membrane electrode assembly of the present invention includes the electrolyte membrane, the solid polymer fuel cell obtained using the same is excellent in power generation characteristics and hydrogen gas utilization efficiency.

Hereinafter, an example of the membrane electrode assembly of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing an example of a membrane electrode assembly of the present invention. The membrane electrode assembly 10 includes: an anode 13 having a catalyst layer 11 and a gas diffusion layer 12, a cathode 14 having a catalyst layer 11 and a gas diffusion layer 12, and an electrolyte membrane 15 disposed between the anode 13 and the cathode 14 in a state of contacting the catalyst layer 11.

Specific examples of the catalyst layer 11 include a layer containing a catalyst and a polymer having an ion exchange group.

Specific examples of the catalyst include: a supported catalyst in which a catalyst containing platinum, a platinum alloy, or platinum having a core-shell structure is supported on a carbon carrier; an iridium oxide catalyst; a catalyst comprising an alloy containing iridium oxide, iridium oxide having a core-shell structure. Carbon black powder is exemplified as the carbon support.

Specific examples of the polymer having an ion exchange group include a polymer H and a perfluoropolymer (hereinafter, also referred to as "polymer H'") which is a polymer other than the polymer H and has an ion exchange group.

The polymer H' preferably contains a unit based on a fluoroolefin and a unit having a sulfonic acid type functional group and a fluorine atom. It is to be noted that the polymer H' may contain units other than them.

Examples of the fluoroolefin include TFE, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and hexafluoropropylene, and TFE is particularly preferable. The fluorine-containing olefin may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The unit having a sulfonic acid functional group and a fluorine atom is preferably a unit represented by the formula (1-1), a unit represented by the formula (1-2) or a unit represented by the formula (1-3).

The number of units having a sulfonic acid functional group and a fluorine atom may be 1 or 2 or more.

Formula (1-1) - [ CF ]₂-CF(-O-R^f1-SO₃M)]-

Formula (1-2) - [ CF ]₂-CF(-R^f1-SO₃M)]-

R^f1Being optionally containing oxygen atoms between carbon atoms and carbon atomsA perfluoroalkylene group. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, and preferably 20 or less, particularly preferably 10 or less.

R^f2Is a single bond or a perfluoroalkylene group optionally containing oxygen atoms between carbon atoms. The number of carbon atoms in the perfluoroalkylene group is preferably 1 or more, particularly preferably 2 or more, and preferably 20 or less, particularly preferably 10 or less.

r is 0 or 1.

M is a hydrogen atom, an alkali metal or a quaternary ammonium cation.

Specific examples of the unit (1-1) include the following units 1-1-1 to 1-1-3. Wherein w is an integer of 1 to 8, and x is an integer of 1 to 5. M in the formula is as defined above.

-[CF₂-CF(-O-(CF₂)_w-SO₃M)]-formula (1-1-1)

-[CF₂-CF(-O-CF₂CF(CF₃)-O-(CF₂)_w-SO₃M)]-formula (1-1-2)

-[CF₂-CF(-(O-CF₂CF(CF₃))_x-SO₃M)]-formula (1-1-3)

Specific examples of the unit (1-2) include the following units. Wherein w is an integer of 1 to 8. M in the formula is as defined above.

-[CF₂-CF(-(CF₂)_w-SO₃M)]-formula (1-2-1)

-[CF₂-CF(-CF₂-O-(CF₂)_w-SO₃M)]-formula (1-2-2)

As the unit (1-3), a unit represented by the following formula (1-3-1) is preferable. M in the formula is as defined above.

In the formula (1-3-1), R^f4Is a linear perfluoroalkylene group having 1 to 6 carbon atoms, R^f5A straight-chain perfluoroalkylene group having 1 to 6 carbon atoms, which is a single bond or optionally contains an oxygen atom between carbon atoms. r and M are as defined above.

The value (Hc-Hk) obtained by subtracting the hydrogen gas permeability coefficient (hereinafter, also referred to as "Hk") of the polymer electrolyte included in the electrolyte membrane from the hydrogen gas permeability coefficient (hereinafter, also referred to as "Hc") of the polymer having ion exchange groups in the catalyst layer of the cathode is preferably 1.0 × 10^-8cm³·cm/(s·cm²cmHg) or more, and more preferably 1.3X 10^-8cm³·cm/(s·cm²cmHg) or more, and more preferably 1.5X 10^-8cm³·cm/(s·cm²cmHg) or more, particularly preferably 1.7X 10^-8cm³·cm/(s·cm²cmHg) or more.

The upper limit of the above-mentioned Hc-Hk value is preferably as high as possible, but is not particularly limited, and is, for example, 2.5X 10^-8cm³·cm/(s·cm²·cmHg)。

If the value of Hc-Hk is within the above range, the power generation characteristics of the PEFC are further improved. The reason for this is not completely clear, and is presumed to be for the following reason.

When the hydrogen permeability coefficient is low, the permeation amount of hydrogen decreases, but the permeation amount of oxygen also tends to decrease. Therefore, if Hc in the cathode to which the oxygen-containing gas is supplied is low, the supply of oxygen to the surface of the catalyst, which is a reaction site, is inhibited.

In view of this problem, if the value Hc-Hk is within the above range, it is possible to suppress crossover of hydrogen gas generated from the anode to the cathode and to promote supply of oxygen gas to the catalyst surface in the cathode side catalyst layer, and therefore it is estimated that: by the synergistic effect of these, a polymer electrolyte fuel cell having more excellent power generation characteristics can be obtained.

The hydrogen gas permeability coefficient of the polymer having ion exchange groups in the catalyst layer of the cathode was determined by the method described in the section of example below.

The gas diffusion layer 12 has a function of uniformly diffusing gas in the catalyst layer and a function as a current collector. Specific examples of the gas diffusion layer include carbon paper, carbon cloth, carbon felt, and a titanium porous body (specifically, a sintered body of titanium particles or fibers).

In order to prevent adhesion of generated gas, the gas diffusion layer may be subjected to water repellency or hydrophilization treatment using PTFE or the like, or hydrophilization using a polymer having an ion exchange group or the like.

The membrane electrode assembly of fig. 1 includes the gas diffusion layer 12, but the gas diffusion layer is an optional member and may not be included in the membrane electrode assembly.

The electrolyte membrane 15 is an electrolyte membrane (solid polymer electrolyte membrane) containing the above polymer electrolyte.

The anode 13 and the cathode 14 may have other components than those described above.

As a specific example of the other member, a carbon layer (not shown) provided between the catalyst layer 11 and the gas diffusion layer 12 is exemplified. If the carbon layer is disposed, the gas diffusivity of the surface of the catalyst layer 11 is improved, and the power generation performance of the fuel cell can be further improved.

The carbon layer includes, for example, carbon and a nonionic fluoropolymer. Specific examples of the carbon include carbon nanofibers having a fiber diameter of 1 to 1000nm and a fiber length of 1000 μm or less. Specific examples of the nonionic fluorine-containing polymer include PTFE.

Specific examples of the method for producing a membrane electrode assembly include: a method of forming a catalyst layer on an electrolyte membrane and further sandwiching the resultant joined body with a gas diffusion layer; and a method in which a catalyst layer is formed on a gas diffusion layer to form electrodes (anode and cathode), and an electrolyte membrane is sandwiched between the electrodes.

The method for producing the catalyst layer includes a method of applying a coating liquid for forming the catalyst layer to a predetermined position and drying the coating liquid as necessary. The coating liquid for forming a catalyst layer is a liquid obtained by dispersing a polymer having an ion exchange group and a catalyst in a dispersion medium.

[ Polymer electrolyte Fuel cell ]

The polymer electrolyte fuel cell of the present invention comprises the membrane electrode assembly.

The polymer electrolyte fuel cell of the present invention comprises the membrane electrode assembly, and therefore has excellent power generation characteristics and hydrogen gas utilization efficiency.

The polymer electrolyte fuel cell of the present invention may have separators in which grooves serving as gas flow paths are formed on both surfaces of the membrane electrode assembly.

Specific examples of the separator include a metal separator, a carbon separator, a separator made of a material in which graphite and a resin are mixed, and a separator made of various conductive materials.

In a polymer electrolyte fuel cell, power is generated by supplying an oxygen-containing gas to a cathode and a hydrogen-containing gas to an anode.

Examples

The present invention will be described in detail below with reference to examples. Examples 6-1 to 6-8 and 7-1 to 7-10 are examples of the present invention, and examples 6-9 to 6-16 and examples 7-11 to 7-18 are comparative examples. However, the present invention is not limited to these examples. The amounts of the respective components added in the following table represent mass standards.

[¹H-NMR]

¹H-NMR at frequency: 300.4MHz, chemical shift standard: the assay was performed under tetramethylsilane conditions. As the solvent, CD is used unless otherwise specified ₃And (C) CN. Quantitative determination of product¹The analysis result of H-NMR was carried out based on the amount of the internal standard sample (1, 3-bis (trifluoromethyl) benzene) added.

[¹⁹F-NMR]

¹⁹F-NMR at frequency: 282.7MHz, solvent: CD (compact disc)₃CN, chemical shift standard: CFCl₃Under the conditions of (1). Quantitative determination of product¹⁹F-NMR analysis and the amount of an internal standard sample (1, 3-bis (trifluoromethyl) benzene) added.

[¹³C-NMR]

¹³C-NMR at frequencyRate: 75.5MHz, chemical shift standard: the assay was performed under tetramethylsilane conditions. Unless otherwise specified, CD is used as a solvent₃CN。

[ ion exchange Capacity ]

The polymer F or the film of the polymer F' was dried under vacuum at 120 ℃ for 12 hours. After measuring the mass of the dried polymer film, the polymer film was immersed in a 0.85 mol/g sodium hydroxide solution (solvent: water/methanol: 10/90 (mass ratio)) at 60 ℃ for 72 hours or more, and then subjected to SO treatment₂And F is hydrolyzed. The ion exchange capacity of the polymer F or the polymer F' was determined by back-titration of the hydrolyzed sodium hydroxide solution with 0.1 mol/L hydrochloric acid. In the present specification, the ion exchange capacity of the polymer H or the polymer H 'as the polyelectrolyte is described to be the same as the ion exchange capacity measured by using the polymer F or the polymer F' as the precursor.

[ proportions of the respective units ]

The proportion of each unit in the polymer F or the polymer F 'is calculated from the ion exchange capacity of the polymer F or the polymer F'.

The proportion of each unit in polymer H or polymer H 'is the same as the proportion of the corresponding unit in polymer F or polymer F'.

[ Hydrogen gas permeability coefficient ]

The hydrogen gas permeability coefficient was measured according to JIS K7126-2: 2006 for a film (film thickness 25 μm) formed of polymer H or polymer H' as a polymer electrolyte. As the measuring apparatus, a gas permeability measuring apparatus (GTR-100 XFAG, manufactured by GTR TEC Co., Ltd.) was used.

The effective transmission area is 9.62cm²The membrane made of the polymer H or the polymer H' of (1) was maintained at 80 ℃, and hydrogen gas having a relative humidity adjusted to 10% was passed through the first surface at 30 mL/min, and argon gas having a relative humidity adjusted to 10% was passed through the second surface at 30 mL/min. The hydrogen gas gradually permeating into argon gas was detected by gas chromatography, and the hydrogen gas permeation amount was calculated in terms of a volume of 1 atm at 25 ℃. The hydrogen permeability was used to determine the amount per 1cm²Membrane area, pressure of permeated gas per 1cmHgThe hydrogen gas permeability was determined as a value obtained by converting the permeability of a gas that permeates at 1 second to a film thickness of 1 cm. The reference dimensions and film thickness of the films used were calculated at temperatures: 23 ℃ and relative humidity: the measurement was performed under the condition of 50% RH.

[ initial Power Generation characteristics ]

The membrane electrode assembly was assembled into a power generation cell, the temperature of the membrane electrode assembly was maintained at 95 ℃, hydrogen gas (utilization rate of 70%) was pressurized to 151kPa (absolute pressure) and supplied to the anode, and air (utilization rate of 50%) was pressurized to 151kPa (absolute pressure) and supplied to the cathode, respectively. As to the degree of humidification of the gas, both hydrogen and air were set to relative humidities of 20% RH, and the recording current density was 2A/cm²The cell voltage at the time was evaluated according to the following criteria. The higher the cell voltage, the more excellent the power generation characteristics of the polymer electrolyte fuel cell.

Very excellent: the cell voltage is 0.43V or more.

Very good: the cell voltage is 0.40V or more and less than 0.43V.

O: the cell voltage is 0.37V or more and less than 0.40V.

X: the cell voltage is less than 0.37V.

[ leakage amount of Hydrogen gas ]

The amount of leakage of hydrogen gas that permeated through the electrolyte membrane of the membrane electrode assembly from the anode side to the cathode side was quantified as the oxidation current value of hydrogen gas on the cathode side by linear sweep voltammetry. The test was carried out as follows: hydrogen (0.05mL/min) and nitrogen (0.2mL/min) were supplied to the anode and cathode, respectively, at atmospheric pressure, and the cell temperature: relative humidity of hydrogen and nitrogen at 80 ℃: the potential on the cathode side was scanned from 0.05V to 0.5V at a scanning rate of 0.5mV/sec using the anode side as a reference electrode under the condition of 100% RH. In the obtained relationship between the current density and the potential, the intercept value of a linear approximation formula in the range of 0.4 to 0.5V was evaluated as the hydrogen leakage current value according to the following criteria. The smaller the hydrogen leakage current value, the more excellent the hydrogen gas utilization efficiency of the polymer electrolyte fuel cell.

Very good: the hydrogen leakage current value is 2.5mA/cm²The following.

O: the hydrogen leakage current value exceeds 2.5mA/cm²And is 4.0mA/cm²The following.

X: the hydrogen leakage current value exceeds 4.0mA/cm²。

[ film thickness ]

The polymer electrolyte membrane was measured by a Digimatic Indicator (ID-C112 XB, manufactured by MITUTOYO), and the average membrane thickness was determined by arithmetically averaging the membrane thicknesses at arbitrary 6 points. The film thickness is measured at a temperature: 23 ℃ and relative humidity: the measurement was performed under the condition of 50% RH.

[ TQ value ]

The polymer F or F' was melt-extruded under an extrusion pressure of 2.94MPa (gauge pressure) at a flow tester (CFT-500A, manufactured by Shimadzu corporation) having a nozzle with a length of 1mm and an inner diameter of 1mm while changing the temperature. The extrusion amount of the polymer F or F' was determined to be 100mm³Temperature per second (TQ value). The higher the TQ value, the higher the molecular weight of the polymer.

[ glass transition temperature ]

For the film of the polymer F or F', a dynamic viscoelasticity measurement apparatus (DVA-225, manufactured by IT measurement and control corporation) was used to measure the thickness of the film in the sample width: 5.0mm, length between clamps: 15mm, measurement frequency: 1Hz, temperature rise rate: the dynamic viscoelasticity was measured at 2 ℃ per minute under the conditions of the stretching mode. Tan δ (loss tangent) was calculated from the ratio (E "/E ') of the loss elastic modulus E ″ to the storage modulus E', and a tan δ -temperature curve was prepared. The glass transition temperature (Tg) of the polymer F or F' is determined by taking the value obtained by reading the peak temperature between-100 ℃ and 200 ℃ from the tan delta-temperature curve.

[ abbreviation ]

TFE: tetrafluoroethylene, tetrafluoroethylene,

PSVE：CF₂＝CFOCF₂CF(CF₃)OCF₂CF₂SO₂F、

PFtBPO：(CF₃)₃COOC(CF₃)₃、

AIBN：(CH₃)₂C(CN)N＝NC(CH₃)₂(CN)、

HFC-52-13p：CF₃(CF₂)₅H、

HFE-347pc-f：CF₃CH₂OCF₂CF₂H、

HCFC-225cb：CClF₂CF₂CHClF、

HCFC-141b：CH₃CCl₂F。

[ example 1]

< example 1-1>

Into a 2L 4-neck flask equipped with a stirrer, a condenser, a thermometer and a dropping funnel, 560g of chlorosulfonic acid was charged under a nitrogen-sealed atmosphere. The flask was cooled in an ice bath, and a mixture of 139.5g of compound 1-1 and 478.7g of methylene chloride was added dropwise over 20 minutes while keeping the internal temperature at 20 ℃ or lower. An exotherm and gas generation was observed upon dripping. After completion of the dropwise addition, the flask was placed in an oil bath, and the reaction was carried out for 7 hours while maintaining the internal temperature at 30 to 40 ℃. The reaction proceeded while gas was generated, and a white solid precipitated. After the reaction, the flask was depressurized to distill off dichloromethane. A yellowish white solid remained in the flask. By passing¹As a result of analysis of the solid by H-NMR, it was confirmed that Compound 2-1 was produced.

NMR spectrum of Compound 2-1;

¹H-NMR (solvent: D)₂O)：4.27ppm(-CH₂-、4H、s)。

¹³C-NMR (solvent: D)₂O)：62.6ppm(-CH₂-)、195.3ppm(C＝O)。

< examples 1 and 2>

The compound 2-1 obtained in example 1-1 was used without isolation in the next reaction. 2049g of thionyl chloride was added to the flask of example 1-1. The flask was heated to 80 ℃ for 15 hoursAnd (4) streaming. As the reaction proceeded, the reflux temperature rose from 52 ℃ to 72 ℃. The generation of gas was confirmed in the reaction. The point at which the compound 2-1 was completely dissolved and the generation of gas was completed was defined as the end point of the reaction. The reaction solution was transferred to a 2L separable flask, and the gas phase portion was sealed with nitrogen gas and allowed to cool naturally for 9 hours, whereby a blackish brown solid precipitated in the separable flask. Unreacted thionyl chloride was removed by decantation. The precipitated solid was washed with toluene and the toluene was removed again by decantation. The toluene washing was carried out 3 times in total, and the total amount of toluene used was 1207 g. The precipitated solid was dried at 25 ℃ for 71 hours under a nitrogen stream. Recovering the dried solid and passing ¹As a result of analysis by H-NMR, 356.5g of Compound 3-1 having a purity of 96.2% was obtained. The yield based on the compound 1-1 was 56.0%.

NMR spectrum of Compound 3-1;

¹H-NMR：5.20ppm(-CH₂-、4H、s)。

¹³C-NMR：72.3ppm(-CH₂-)、184.6ppm(C＝O)。

< examples 1 to 3>

In a 1L 4-neck flask equipped with a stirrer, condenser and thermometer, 90.0g of compound 3-1 and 750mL of acetonitrile were charged under a nitrogen-sealed atmosphere. While the flask was cooled in an ice bath, 110.3g of potassium hydrogen fluoride was added thereto with stirring. A slight exotherm with the addition occurred. The ice bath was changed to a water bath, and the reaction was carried out for 62 hours while maintaining the internal temperature at 15 to 25 ℃. As the reaction proceeds, a fine white solid is formed. The reaction solution was transferred to a pressure filter, and unreacted potassium hydrogen fluoride and the product were filtered off. Acetonitrile was added to the filter, and the solid obtained by filtration was washed until the filtrate became transparent, and the washing solution was recovered. The filtrate and the washing solution were distilled off by an evaporator to remove acetonitrile. 950mL of toluene was added to the solid remaining after drying, and the solid was dissolved in toluene by heating to 100 ℃. Subjecting the solution to natural treatmentThe undissolved components were removed by filtration. The filtrate was transferred to a 1L separable flask, and the gas phase portion was sealed with nitrogen gas and naturally cooled for 14 hours, whereby pale brown needle-like crystals were precipitated in the separable flask. The crystals were washed with toluene and dried under a stream of nitrogen at 25 ℃ for 30 hours. Recovering the dried solid by ¹H-NMR and¹⁹F-NMR analysis showed that 58.1g of compound 4-1 with a purity of 97.6% was obtained. The yield based on the compound 3-1 was 72.3%.

NMR spectrum of Compound 4-1;

¹H-NMR：4.97ppm(-CH₂-、4H、d、J＝3.1Hz)。

¹⁹F-NMR：62.4ppm(-SO₂F、2F、t、J＝3.1Hz)。

¹³C-NMR：60.7ppm(-CH₂-)、184.9ppm(C＝O)。

< examples 1 to 4>

Into a 200mL autoclave made of nickel, 9.93g of Compound 4-1 and 89.7g of acetonitrile were charged. The autoclave was cooled, and nitrogen gas was supplied at a flow rate of 6.7L/hr while maintaining the internal temperature at 0 to 5 ℃ to bubble the reaction solution for 1 hour. While maintaining the temperature of the reaction solution at 0 to 5 ℃, a mixed gas of fluorine gas and nitrogen gas (mixing ratio: 10.3 mol%/89.7 mol%) was introduced at a flow rate of 6.7L/hr for 6 hours. Nitrogen gas was again supplied at a flow rate of 6.7L/hr, and the reaction solution was bubbled for 1 hour. 103.2g of the reaction solution was recovered from the autoclave. By passing¹⁹Quantitative analysis of the reaction mixture by F-NMR confirmed that the reaction mixture contained 8.4 mass% of Compound 5-1. The reaction yield based on the compound 4-1 was 66%.

NMR spectrum of Compound 5-1;

¹⁹F-NMR：-104.1ppm(-CF₂-、4F、s)、45.8ppm(-SO₂F、2F、s)。

< examples 1 to 5>

Into a 200mL autoclave made of nickel, 19.9g of Compound 4-1 and 85.6g of acetonitrile were charged. The autoclave was cooled, and nitrogen gas was supplied at a flow rate of 6.7L/hr while maintaining the internal temperature at 0 to 5 ℃ to bubble the reaction solution for 1 hour. While maintaining the temperature of the reaction solution at 0 to 5 ℃, a mixed gas of fluorine gas and nitrogen gas (mixing ratio: 10.3 mol%/89.7 mol%) was introduced at a flow rate of 16.4L/hr for 6.5 hours. Nitrogen gas was again supplied at a flow rate of 6.7L/hr, and the reaction solution was bubbled for 1 hour. 109.6g of a reaction solution containing Compound 5-1 was recovered from the autoclave.

< examples 1 to 6>

Into a 200mL autoclave made of nickel, 20.1g of Compound 4-1 and 80.1g of acetonitrile were charged. The autoclave was cooled, and nitrogen gas was supplied at a flow rate of 6.7L/hr while maintaining the internal temperature at 0 to 5 ℃ to bubble the reaction solution for 1 hour. While maintaining the temperature of the reaction solution at 0 to 5 ℃, a mixed gas of fluorine gas and nitrogen gas (mixing ratio: 20.0 mol%/80.0 mol%) was introduced at a flow rate of 8.4L/hr for 6 hours. Nitrogen gas was again supplied at a flow rate of 6.7L/hr, and the reaction solution was bubbled for 1 hour. 107.1g of a reaction solution containing Compound 5-1 was recovered from the autoclave.

< examples 1 to 7>

In a 50mL 4-neck flask equipped with a stirrer, a condenser, a thermometer and a dropping funnel, 1.65g of potassium fluoride and 7.8mL of diethylene glycol dimethyl ether (diglyme) were charged. 8.43g of the reaction solution obtained in example 1-4 was added dropwise using a plastic syringe while cooling the flask in an ice bath and stirring to keep the internal temperature at 0 to 10 ℃. A strong exotherm was observed and 15 minutes was required for dropwise addition. And after the dropwise addition, changing the ice bath into a water bath, and carrying out reaction for 1 hour at 15-20 ℃. The reaction mixture was cooled again in an ice bath, and 6.56g of Compound 6-1 was added dropwise from the dropping funnel while maintaining the temperature of the reaction mixture at 0 to 10 ℃. After the dropwise addition, the ice bath was changed to a water bath, and the reaction was carried out at 20 to 25 ℃ for 3.5 hours. Removing by-product solid from the reaction solution by suction filtration, Recovering the filtrate. The filtered residual solid was washed with an appropriate amount of acetonitrile, and a washing liquid was mixed with the filtrate. By passing¹⁹F-NMR quantitative analysis of 37.1g of the filtrate revealed that 2.04% by mass of Compound 7-1 was contained. The reaction yield based on the compound 4-1 was 46.6%.

NMR spectrum of Compound 7-1;

¹⁹F-NMR：-191.5ppm(CF₂＝CF-、1F、ddt、J＝116、38、14Hz)、-133.8ppm(-O-CF-、1F、tt、J＝21.3、6.1Hz)、-103.1ppm(-CF₂-SO₂F、4F、m)、-101.5ppm(CF₂＝CF-、1F、ddt、J＝116、49、27Hz)、-87.6ppm(CF₂＝CF-、1F、ddt、J＝49、38、7Hz)、-67.5ppm(-CF₂-O-、2F、m)、46.8ppm(-SO₂F、2F、s)。

< examples 1 to 8>

Into a 500mL 4-neck flask equipped with a stirrer, a condenser, a thermometer and a dropping funnel were charged 36.6g of potassium fluoride and 125.6g of acetonitrile. 79.8g of the reaction solution obtained in examples 1 to 5 was added dropwise to the flask using a plastic dropping funnel while cooling the flask in an ice bath and stirring the mixture to maintain an internal temperature of 0 to 10 ℃. A strong exotherm was observed and 23 minutes was required for dropwise addition. And after the dropwise addition, the ice bath is changed into a water bath, and the reaction is carried out for 5.5 hours at the temperature of 20-30 ℃. After cooling again in an ice bath, 146.0g of Compound 6-1 was added dropwise from the dropping funnel while keeping the temperature of the reaction mixture at 0 to 10 ℃. And after the dropwise addition is finished, changing the ice bath into a water bath, and carrying out reaction for 16 hours at 15-25 ℃. Suction filtration was carried out in the same manner as in examples 1 to 7, and the filtrate was passed through¹⁹F-NMR quantitative analysis was carried out on 412.3g of the obtained filtrate, and it was confirmed that compound 7-1 was contained in an amount of 3.93 mass%. The reaction yield based on the compound 4-1 was 55.9%. The filtrate was subjected to distillation under reduced pressure, whereby Compound 7-1 was isolated as a fraction having a boiling point of 97.2 ℃ C/10 kPa. The purity by gas chromatography was 98.0%.

< examples 1 to 9>

In a 50mL 4-neck flask equipped with a stirrer, a condenser, a thermometer and a dropping funnel, 3.70g of potassium fluoride and 10.9g of acetonitrile were charged. 10.2g of the reaction solution obtained in examples 1 to 6 was dropped using a plastic syringe while the flask was cooled and stirred under ice bath to maintain the internal temperature at 0 to 10 ℃. A strong exotherm was observed and the dropwise addition required 8 minutes. And after the dropwise addition, changing the ice bath into a water bath, and carrying out reaction for 3 hours at the temperature of 20-30 ℃. Then, the reaction mixture was cooled again in an ice bath, and 14.6g of compound 6-1 was added dropwise from the dropping funnel while keeping the temperature of the reaction mixture at 0 to 10 ℃. After the dropwise addition, the ice bath is changed into a water bath, and the reaction is carried out for 17 hours at 15-25 ℃. Suction filtration was carried out in the same manner as in examples 1 to 7, and the filtrate was passed through¹⁹F-NMR quantitative analysis of 55.9g of the obtained filtrate confirmed that the filtrate contained 4.77% by mass of Compound 7-1. The reaction yield based on the compound 4-1 was 69.6%. The reaction yield based on the compound 1-1 (reaction yield in the whole monomer synthesis step) was 28.2%.

[ example 2]

(example 2-1)

70.0g of Compound 7-1 was placed in an autoclave (internal volume 100mL, made of stainless steel), and the autoclave was cooled with liquid nitrogen and degassed. 2.53g of TFE was introduced into the autoclave, and the autoclave was heated in an oil bath until the internal temperature became 100 ℃. The pressure at this time was 0.29MPaG (gauge pressure). A mixture of 36.3mg of PFtBPO and 2.58g of HFC-52-13p as a polymerization initiator was introduced into the autoclave by pressure. Further, nitrogen gas was introduced from the pressure line to completely squeeze the pressure liquid in the pressure line. By this operation, TFE in the gas phase part was diluted, and as a result, the pressure was increased to 0.56 MPaG. Polymerization was carried out by continuously adding TFE while maintaining the pressure at 0.56 MPaG. When the amount of TFE added was 4.03g over 9.5 hours, the polymerization was stopped by cooling the inside of the autoclave, and the gas in the system was purged. The reaction mixture was diluted with HFC-52-13p, and HFE-347pc-f was added to aggregate the polymer, followed by filtration. Thereafter, the operation of stirring the polymer in HFC-52-13p and reaggregating it in HFE-347pc-f was repeated 2 times. Vacuum drying at 120 ℃ gave a copolymer of TFE and compound 7-1, i.e., polymer F-1. The obtained polymer F-1 was used to measure the above-mentioned various physical properties. The results are shown in Table 1.

(example 2-2)

The conditions of example 2-1 were changed as shown in Table 1. In example 2-2, instead of the initial charging of TFE, TFE was heated to a polymerization temperature and then TFE was bubbled up to a pressure before dilution with nitrogen as shown in Table 1. Otherwise, a polymer F-2 was obtained in the same manner as in example 2-1. The obtained polymer F-2 was used to measure the above-mentioned various physical properties. The results are shown in Table 1.

[ Table 1]

[ example 3]

< example 3-1>

Using the polymer F-1, a film of the polymer H-1 was obtained by the following method.

Polymer F-1 was press-molded at a temperature 10 ℃ higher than the TQ value and under a pressure of 4MPa (gauge pressure) to obtain a film of polymer F-1. The film of the polymer F-1 was immersed in an aqueous alkali solution a (potassium hydroxide/water: 20/80 (mass ratio)) at 80 ℃ for 16 hours to prepare polymer F-1 with — SO₂F is hydrolyzed and converted into-SO₃K. The polymer film was immersed in 3 mol/L hydrochloric acid aqueous solution at 50 ℃ for 30 minutes, and then immersed in 80 ℃ ultrapure water for 30 minutes. A total of 5 cycles of immersion in aqueous hydrochloric acid and immersion in ultrapure water were carried out, the-SO of the polymer being introduced₃Conversion of K to-SO₃H. The washing with ultrapure water was repeated until the pH of the water of the polymer-impregnated film became 7. The polymer film was sandwiched by filter paper and air-dried to obtain a polymer H-1 film.

< example 3-2>

A film of polymer H-2 was obtained in the same manner as in example 3-1, except that polymer F-2 was used instead of polymer F-1 and aqueous alkali solution C (potassium hydroxide/methanol/water: 15/20/65 (mass ratio)) was used instead of aqueous alkali solution a.

[ example 4]

< example 4-1>

An autoclave made of Hastelloy having an internal volume of 230mL was charged with PSVE 123.8g, HCFC-225cb 35.2g, and AIBN 63.6mg, cooled with liquid nitrogen, and degassed. TFE was introduced into the system while the temperature was increased to 70 ℃ to maintain the pressure at 1.14MPa (gauge pressure). TFE was continuously added so that the pressure was constant at 1.14MPa (gauge pressure). After 7.9 hours had elapsed, the autoclave was cooled to a point where the amount of TFE added was 12.4g, and the reaction was terminated by purging the gas in the system. The polymer solution was diluted with HCFC-225cb, and HCFC-141b was added thereto to aggregate the polymer solution. The polymer F '-1 was washed with HCFC-225cb and HCFC-141b and dried to obtain 25.1g of a polymer F' -1 which is a copolymer of TFE and PSVE. The results are shown in Table 2.

[ Table 2]

[ example 5]

< example 5-1>

A film of the polymer H '-1 was obtained in the same manner as in example 3-1, except that the polymer F' -1 was used in place of the polymer F-1.

[ example 6]

< example 6-1>

A100 mL Polytetrafluoroethylene (PTFE) container was charged with 4.3g of a finely cut polymer H-1 film and 75g of ultrapure water, and heated at 200 ℃ for 24 hours. The contents were transferred to a PTFE cylinder and allowed to air dry at 30 ℃ for 64 hours under a nitrogen atmosphere. The dried polymer H-1 was transferred to a 200mL glass autoclave, and 21.4g of a mixed solvent of ultrapure water and ethanol (50/50 (mass ratio)) was added thereto. After stirring at 110 ℃ for 25 hours, 3.87g of ultrapure water was added thereto for dilution. After stirring at 90 ℃ for 5 hours, the mixture was naturally cooled and filtered by means of a pressure filter (filter paper: PF040 manufactured by ADVANTEC TOYO Co., Ltd.), whereby 31.9g of a liquid composition S-1 in which a polymer H-1 was dispersed in a mixed solvent was obtained.

The liquid composition S-1 was applied to a 100 μm ethylene-tetrafluoroethylene copolymer (ETFE) sheet by a die coater to form a film, which was dried at 80 ℃ for 15 minutes and further subjected to heat treatment at 185 ℃ for 30 minutes to obtain a solid polymer electrolyte membrane 1 formed of a polymer H film as an electrolyte. The amount of the liquid composition applied was adjusted so that the film thickness of the solid polymer electrolyte membrane became the value shown in tables 3-1 to 3-2. The results are shown in Table 3-1.

< example 6-2 to example 6-16>

Solid polymer electrolyte membranes 2 to 16 each formed of a polymer H or H 'were obtained in the same manner as in example 6-1 except that a liquid composition was prepared using the polymer H or the polymer H' shown in tables 3-1 to 3-2 in place of the polymer H-1, and the amount of the liquid composition applied was adjusted so that the membrane thickness of the solid polymer electrolyte membrane became the value shown in tables 3-1 to 3-2. The results are shown in tables 3-1 to 3-2.

[ Table 3-1]

[ tables 3-2]

In tables 3-1 to 3-2, the description of "2.10E-09" and the like is abbreviated as an index. As a specific example thereof, "2.10E-09" means "2.10X 10^-9". The same applies to tables 4-1 to 4-2 described below.

[ example 7]

< example 7-1>

The polymer H '-1 and an ethanol/water mixed solvent (60/40 (mass ratio)) were mixed to obtain a polymer H' -1 dispersion liquid having a solid content concentration of 25.8 mass%.

To 44g of a supported catalyst (manufactured by Takara Shuzo Co., Ltd.) in which 46 mass% of platinum was supported on carbon powder, 221.76g of water and 174.24g of ethanol were added, and the mixture was mixed and pulverized by an ultrasonic homogenizer to obtain a catalyst dispersion. 80.16g of a polymer H' -1 dispersion and 44.4g of ethanol were added to the catalyst dispersion25.32g of ZeORA-H (manufactured by ZEON corporation, Japan) was previously mixed and kneaded to obtain 102.06g of a mixed solution, 26.77g of water and 12g of ethanol were further added thereto, and the mixture was mixed by an ultrasonic homogenizer so that the solid content concentration was 10% by mass to obtain a coating liquid for forming a catalyst layer. The resulting solution was applied to an ETFE sheet by a die coater, dried at 80 ℃ and further subjected to heat treatment at 160 ℃ for 30 minutes to form platinum in an amount of 0.4mg/cm²The catalyst layer of (1).

81.6g of ethanol and 154.4g of distilled water were added to 50g of vapor grown carbon fiber (product name: VGCF-H, manufactured by Showa Denko K.K., fiber diameter: about 150nm, fiber length: 10 to 20 μm) and sufficiently stirred. To this, 89g of a polymer H '-1 dispersion obtained by mixing a polymer H' -1 and an ethanol/water mixed solvent (60/40 (mass ratio)) at a solid content concentration of 28.1% was added, sufficiently stirred, and further mixed and pulverized by an ultrasonic homogenizer to prepare an intermediate layer forming coating liquid.

The coating liquid for forming an intermediate layer was made to have a solid content of 3mg/cm by using a die coater²The coating was applied to the surface of a gas diffusion substrate (NOK, trade name: X0086T 10X13), and dried at 80 ℃ to prepare an interlayer-equipped gas diffusion substrate having an interlayer formed on the surface of a carbon nonwoven fabric.

The solid polymer electrolyte membrane 1 was sandwiched between two ETFE sheets with catalyst layers from both sides, heated and pressurized at a pressurizing temperature of 160 ℃ for 2 minutes under a pressure of 3MPa, the catalyst layers were bonded to both sides of the solid polymer electrolyte membrane 1, and the ETFE film was peeled off from the catalyst layers to obtain an electrode area of 25cm²The membrane catalyst layer assembly of (1).

In the membrane catalyst layer-bonded body, a gas diffusion substrate with a carbon layer (trade name: X0086 IX92 CX320, manufactured by NOK) was disposed on the anode side and a gas diffusion substrate with an intermediate layer was disposed on the cathode side so that the carbon layer and the intermediate layer were in contact with the catalyst layer side. The membrane electrode assembly was heated and pressurized at a pressurizing temperature of 160 ℃, a pressurizing time of 2 minutes, and a pressure of 3MPa, to thereby prepare a membrane electrode assembly for initial power generation characteristic evaluation and hydrogen leakage evaluation. The results are shown in Table 4-1.

< example 7-2 to example 7-8, example 7-11 to example 7-18>

A membrane electrode assembly for initial power generation characteristic evaluation and hydrogen leakage evaluation was fabricated in the same manner as in example 7-1, except that the solid polymer electrolyte membranes 2 to 16 described in tables 3-1 to 3-2 were used in place of the solid polymer electrolyte membrane 1 obtained in example 6-1. The results are shown in tables 4-1 to 4-2.

< examples 7 to 9>

A membrane electrode assembly to be used for the initial power generation characteristic evaluation and the hydrogen leakage evaluation was prepared in the same manner as in example 7-1 except that the solid polymer electrolyte membrane 8 shown in Table 3-1 was used in place of the solid polymer electrolyte membrane 1 obtained in example 6-1, a polymer H '-2 dispersion shown below was used in place of the polymer H' -1 dispersion used for preparing the coating liquid for catalyst layer formation, and the amount of addition was adjusted so that the mass ratio of the polymer of the coating liquid for catalyst layer formation to the catalyst carrier was not changed. The results are shown in Table 4-1.

The polymer H' -2 dispersion was prepared as follows.

459.97g of a monomer represented by formula m32-1 and 79.28g of a monomer represented by formula m22-1 were charged into a stainless steel autoclave having an internal volume of 230mL, and sufficiently degassed under cooling with liquid nitrogen. 22.38g of TFE was charged, the temperature was raised to 22 ℃ and a radical polymerization initiator ((C) dissolved in a solvent (trade name: AC-2000, manufactured by AGC Co., Ltd.) at a concentration of 2.91% by mass was charged ₃F₇COO)₂)161.5mg, the reaction was started by washing the feed line with 2g of AC-2000. After stirring for 24 hours, the autoclave was cooled to stop the reaction.

The product was diluted with AC-2000 and mixed with a mixture of AC-2000: methanol 8:2 (mass ratio), and the polymer was aggregated and filtered. The polymer was washed with a mixture of AC-2000 and methanol at 7:3 (mass ratio), separated by filtration, and the solid content was dried under reduced pressure at 80 ℃ overnight to give polymer (F' -2).

By mixing the obtained polymer (F' -2) in a solvent containing 20 mass% of methanol% and 15 mass% of potassium hydroxide in an aqueous solution at 50 ℃ for 40 hours to thereby control-SO in the polymer (F' -2)₂Hydrolysis of F group to-SO₃And a K group. Subsequently, the polymer was immersed in a 3 mol/L aqueous hydrochloric acid solution at room temperature for 2 hours. Changing the hydrochloric acid aqueous solution, and repeating the same treatment 4 times to obtain-SO in the polymer₃The K group is converted to the sulfonic acid group of the polymer H' -2.

By using¹⁹F-NMR analysis of the composition of the structural units constituting the polymer H ' -2 revealed that the polymer H ' -2 contained 50 mol% of the monomer unit represented by the formula m22-1, 21.3 mol% of the monomer unit represented by the formula m32-1 and 28.7 mol% of the TFE unit, relative to the total units contained in the polymer H ' -2.

The obtained polymer H '-2 was mixed with an ethanol/water mixed solvent (60/40 (mass ratio)) to obtain a polymer H' -2 dispersion liquid having a solid content concentration of 10 mass%.

< examples 7 to 10>

A membrane electrode assembly for initial power generation characteristic evaluation and hydrogen leakage amount evaluation was produced in the same manner as in examples 7 to 9, except that the polymer H '-3 dispersion shown below was used instead of the polymer H' -2 dispersion used for preparing the coating liquid for catalyst layer formation, and the amount of addition was adjusted so that the mass ratio of the polymer to the catalyst carrier in the coating liquid for catalyst layer formation was not changed. The results are shown in Table 4-1.

Polymer H ' -3 was obtained in the same manner as in the synthesis method of Polymer H ' -2, except that the amount of each monomer used in the synthesis of Polymer H ' -2 was adjusted.

By using¹⁹F-NMR analysis of the composition of the structural units constituting the polymer H ' -3 revealed that the content of the monomer unit represented by the formula m22-1 in the polymer H ' -3 was 65 mol% and that in the polymer m32-1, relative to the total units contained in the polymer H ' -3The monomer unit content shown is 17 mol% and the TFE unit content is 18 mol%.

A polymer H '-3 dispersion was obtained in the same manner as in the preparation of the polymer H' -2 dispersion except that the polymer H '-3 was used in place of the polymer H' -2.

[ Table 4-1]

[ tables 4-2]

In tables 4-1 to 4-2, the difference in hydrogen permeability coefficient is: a value (Hc-Hk) obtained by subtracting the hydrogen gas permeability coefficient (hereinafter, also referred to as "Hk") of the polymer electrolyte included in the electrolyte membrane from the hydrogen gas permeability coefficient (hereinafter, also referred to as "Hc") of the polymer having ion exchange groups in the catalyst layer of the cathode.

As shown in tables 3-1 to 3-2 and tables 4-1 to 4-2, when the hydrogen gas permeability coefficient under the conditions of 80 ℃ and 10% relative humidity is 2.4X 10^-9cm³·cm/(s·cm²cmHg) or less and a film thickness of 7 to 20 μm, a polymer electrolyte fuel cell having excellent power generation characteristics and hydrogen gas utilization efficiency can be obtained (examples 6-1 to 6-8 and examples 7-1 to 7-10).

On the other hand, when a solid polymer electrolyte membrane having at least one of the hydrogen gas permeability coefficient and the membrane thickness outside the above-mentioned range is used, at least one of the power generation characteristics and the hydrogen gas utilization efficiency of the solid polymer fuel cell obtained using the membrane is poor (examples 6-9 to 6-16, and examples 7-11 to 7-18).

The entire contents of the specification, claims, drawings and abstract of japanese patent application No. 2019-036477, which was filed on 28.2.2019, are incorporated herein by reference as the disclosure of the present specification.

Industrial applicability

10 membrane electrode assembly

11 catalyst layer

12 gas diffusion layer

13 anode

14 cathode

15 electrolyte membrane

Claims

1. A solid polymer electrolyte membrane comprising a polymer electrolyte having a hydrogen permeability coefficient of 2.4 x 10 at a temperature of 80 ℃ and a relative humidity of 10%^-9cm³·cm/(s·cm²cmHg) or less,

the thickness of the solid polymer electrolyte membrane is 7-20 μm.

2. The solid polymer electrolyte membrane according to claim 1, wherein the polymer electrolyte is a perfluoropolymer having an acid-type sulfonic acid group.

3. The solid polymer electrolyte membrane according to claim 2, wherein the perfluoropolymer comprises a perfluoromonomer unit,

the perfluorinated monomer units comprise at least 1 unit selected from the group consisting of perfluorovinyl ether units and perfluoroallyl ether units.

4. The solid polymer electrolyte membrane according to claim 2 or 3, wherein the perfluoropolymer contains substantially no at least 1 unit selected from the group consisting of a unit having a halogen atom other than a fluorine atom, a unit having a ring structure, and a unit having a crosslinked structure formed by covalent bonds.

5. The solid polymer electrolyte membrane according to claim 3 or 4, wherein the perfluoroallyl ether unit is a unit represented by the formula A-1,

in the formula A-1, R^F1And R^F2Each independently a C1-3 perfluoroalkylene group.

6. The solid polymer electrolyte membrane according to any one of claims 3 to 5, wherein the perfluoromonomer unit further comprises a tetrafluoroethylene unit.

7. The solid polymer electrolyte membrane according to any one of claims 1 to 6, wherein the polymer electrolyte has an ion exchange capacity of 1.4 to 2.5 meq/g of the dried resin.

8. A membrane-electrode assembly comprising: an anode having a catalyst layer, a cathode having a catalyst layer, and the solid polymer electrolyte membrane according to any one of claims 1 to 7 disposed between the anode and the cathode.

9. The membrane electrode assembly according to claim 8, wherein the catalyst layer of the cathode comprises a catalyst and a polymer having an ion exchange group,

the value obtained by subtracting the hydrogen permeability coefficient of the polymer electrolyte from the hydrogen permeability coefficient of the polymer having ion exchange groups was 1.0X 10 ^-8cm³·cm/(s·cm²cmHg) or more.

10. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 8 or 9.